There is actually a lot of science behind the oil-based air freshener. If you make your own, you probably can't help but learn a few things about how the fresheners function, which could easily help you make more effective and better-smelling air fresheners. If you have a reed diffuser, or want to make one for your home, you can easily make the diffuser and some refills with just a few simple oils and a little mixing.
Pour carrier oil into the bottle, filling it to about half of its capacity. A carrier oil comes from the fatty part of a plant, and is called so because it carries the scented oil into the air, or the skin in lotions. For an oil-based air freshener, you want a thin oil, which is nearly watery.
Drip in about 20 drops of your scented oil. When mixed together, the oil will be diluted to release a certain amount of scent. You can add less scent to dilute it more and create a milder scent, or saturate the mixture with more scent for a stronger smell.
Pour in a small amount of vodka. If you have less than 236ml of fluid, about 1 teaspoon is plenty of vodka. The vodka prevents the mixture from evaporating too quickly by raising the boiling point.
Stir the mixture with a single reed stick for a few seconds to mix all of the oils together. Leave the stick in the bottle when finished.
Place the remaining reeds into the mouth of the jar, so that they look scattered. These reeds draw the oils through the capillaries of the reed, and bring them to the surface where the small amounts in the reed evaporate into the air and carry the scent into your home.
Choose oil scents that match the season you are in. For example, give your air freshener a winter holiday twist by using peppermint oil, or oil from an evergreen tree.